Method of making a heat exchanger cross tied pin assembly



Aug. 13, 1963 J. R. GIER, JR 3,100,332

METHOD OF MAKING A HEAT EXCHANGER CROSS TIED PIN ASSEMBLY Filed Feb. 25, 1960 5 Sheets-Sheet 1 95 5a a Z difz 2- #1 1 J- 4 J- 20 20 2 2 2 2 2 9W .2;. a; 2'0 0 0 0 Z I 4 4 F yZ 4 F2 3 5; +5

12 (12 -11 41 Fzy INVENTOR.

J N R G/Ee 7e,

i ATTOEN'K 3,100,332 oss Aug. 13, 1963 J. R. GIER, JR

METHOD OF MAKING A HEAT EXCHANGER CR TIED PIN ASSEMBLY 3 Sheets-Sheet 2.

Filed Feb. 23, 1960 INVENTOR.

IA rmeA/EX Aug. 13, 1963 3,100,332

J. R. GIER, JR METHOD OF MAKING A HEAT EXCHANGER CROSS TIED PIN ASSEMBLY Filed Feb. 23, 1960 3 Sheets-Sheet 3 i527 INVENTOR.

I [rue/var United States Patent 3,100,332 METHOD OF MAKING A HEAT EXCHANGER CROSS TIED PIN ASSEIVIBLY John R. Gier, Jr., Hines Hill Road, Hudson, Ohio Filed Feb.23, 1960, Ser. No. 10,462 4 Claims. (Cl.-29157.3)

the mats to the confining plates between which they are disposed in the heat exchanger.

The present invention, therefore, relates to a specialized form for heat exchanger of the general purposes described in my copending application Serial No. 8,378, filed Febru ary 12, 1960, and is made by a method adapted for its particular specialized production on conventional equipment.

In my US. Letters Patent No. 2,678,808, issued May 18, 1954, a pin fin assembly and a heat exchanger embodying the same are disclosed. As therein disclosed, the pin fin mat comprises a myriad of rows of pins with connecting ligaments between the individual pins of each row, the pins of each row and the rows being disposed in parallel and laterally spaced relation to each other between paral lel fiatwise spaced confining plates with the axes of the pins normal to the plate faces and with the pin ends and liga-. merits brazed to the confining plates.

In the present structure, the pins areindividually formed from relatively stiff, heavy rod or wire stockv which, in lengths as short as the pins, is very rigid and resistant to flexure transversely of its axis. The pins are not connected by ligaments but are tied together, preparatory to assembly into heat exchanger mats, .by cross tie members which secure the pins of each row in proper parallel spaced relation with respect to each other and also secure the'adjacent rows of pins in proper parallel spaced relation. The pins are secured by the tie bars with the endsof the pins exposed for brazing to the confining plates.

The present invention has particular advantages .in those instances in which relatively stiff, heavy pins are required and in which the tie bars must be of relatively stiff material which has a high degree of resistance to fiexure in a direction normal to the plane. of the row of pinsto which they are bonded. i 1

' Furthermore, the resulting structure is one in which the mat, despite its heavy construction, has a degree of flexibility transversely of the rows 'of pins and tie bars such that it can conform more readily to the confining plates 3,100,332 Patented Aug. 13, 1963 trated in FIG. 4, and is taken on the line '5-5 thereof;

FIG. 6 is a diagrammatic illustration of a specific problem presented in connection with the method of the present invention and the solution thereof;

FIG. 7 is a diagrammatic side elevation of an apparatus suitable for carrying out the method of the present invention and illustrating the operations. performed on the pins and cross members thereby; V I

FIG. 8 is a vertical sectional view through the apparatus of FIG. 7, and is taken on the line 8-8 thereof;

FIGS. 9 and 10 are a side elevation'and a right end elevation, respectively, of an apparatus adapted for carrying out a modified method of the present invention; and FIG. 11 is a fragmentary cross sectional view of a heat exchanger illustrating a specialized embodiment of the invention.

Referring to the drawings, the pin fin assembly comprises a plurality of pins 1, each of which is of rod or Wire stock of relatively large cross section which, in lengths used for the pins, is relatively stiff with a very high degree of resistance to fiexure transversely of its axis.

The pins, for purposes of illustration, are shown in FIG. 1 as being circular cross section, about inch in diameter and about 2 inches long, respectively. However, the specific cross sectional shape and diameter is of secondary importance except that the pins are of -a cross section and length such thatthey are relatively stiff. Pins of streamlined or lenticular cross section may be used.

The pins are secured together by cross tie members 2 which may have the same cross sectional area as the pins, but, if desired, may be of lenticular or streamlined cross section as illustrated in FIGS. 1 through 3.

The pins are arranged in rows, the pins of each row being in laterally spaced parallel relation to each other and preferably with the opposite faces of the row planar and parallel to each other.

The cross tie members '2 extend longitudinally of the rows of pins and at their juuctures with the pins which they contact, the pins are embedded therein and welded thereto, the welding and embedding being occasioned concurrently by the proper application of pressure and heat during the welding operation.

The pins of each row are closely spaced with respect to each other in a direction endwise of the row with the result that each cross tie member 2, in the length between any two adjacent pins of a row, is relatively short, so short, in fact, that it is extremely resistant to bending in a direction transversely of the plane of the faces of. the rows. The members 2, if lenticular in cross section, are arranged with the major axes of their cross sections normal to the'planes of the [faces of the rows of pins 3 to which they are connected.

between which it is disposed preparatory to bonding,vthere- 1 by facilitating brazing.

More specifically, the structure is one which can be manufactured readily with conventional equipment.

Various other objects and advantages will become an parent from the following description wherein reference is made to the drawings, in which:

'FIGS. 1, 2, and 3 are, respectively, a top plan view, a

front elevation, and a right end elevation, 0f a heat exchanger embodying the principles of the present invention,

parts thereof being broken away, and parts being shown They are of sufiicient width in the direction of the major axes of their cross sections to space the rows about the same distance apart as the pins of each row are spaced apart from each other. In the form illustrated, the spacing between adjacent edges or faces of two adjacent pins of a row or of adjacent rows is about two to three times the diameter of a pin. The welded bond between the pins of a row and their cross tie member is rigid and unyielding.

- This stiffness of the pins and of the cross tie members gives rise to difiiculties in the manufacture of the mats and in the provision of suitable mats.

As" illustrated, the cross tie members are arranged near the ends of the pins to which they are attached, but

preferably spaced a substantial distance from the ends.

Preferably, only one cross tie member 2 is disposed between adjacent rows of pins, the ends of the pins on posite from the cross tie member between a given pair of rows being free for movement relatively toward each other by flexure of the cross tie member adjacent their between confining plates.

but with alternate cross tie members disposed in alternate spaces between the rows. 7 Thus, in every other' space,

the other face of the mat.

to the cross tie members so thatthe mat can better conform to the confining plates on which it is to be disposed," thereby facilitating brazing to the plates.

The mats thus formedare disposed when used in heat exchangers between heat exchange confining plates such as .walls indicated at 3=and 4,,and the ends of the pins are brazed or otherwise bonded to the walls, as described in other ends. Thus, the rows of pins are arranged with v cross tie members between each pair of adjacent rows one row are disposed with upper face of therow, on a supporting'table so that the cross tie member extends upwardly normal to the plane their cross tie member at the of the table A duplicate row of pins with the cross tie 'member extending upwardly from the plane of the row is disposed thereabove but with the cross tie member positioned at the opposite edge of the rows of pins from the first cross tie member.

For example, as illustrated in FIGS. .7 and 8, a row of pins, indicated at a, is laid on supports -14 and '15, the

connecting cross tie barfb extending upwardlynormal to the plane of the row of'pins a. V

- An additional row of pins/c with a cross tie member -d .is positioned and supported on a guide 16 so as to-lie my US. Letterslatent No. 2,678,808, issued May 18,;

Generally, in heat exchangers, the resulting mat of at 5. Thus, air can be forced through the heat exchanger in a direction either parallel to or transversely of the cross tie members '2, but preferably transversely thereof; that is,

in a direction of spacing of the rows of pins from'each.

other. It is for this reason that the cross tie member 'is made lenti-cular or streamlined in cross section in a direction of spacing of the rows of pins. I

Per constructionpurposes, since thepins-are relatively large and heavy, and the support thereof during welding and installation is thereby rendered difficult, the pins are arranged in asemblies which are joined together to form V a mat. A mat may comprise any number of rows of pins formed by adding successive assemblies each of which comprises one row of pins 1 and one cross tie member 2.

It 1 desired, however, the mats canbe formed of assemblies each of which includes more than one, row of pins. For example, as illustrated in FIG. 4, a simple type of assembly is one, such as generally described above, in which each outer-most face of two rows of pins 1*1 connected to a common cross tie member '12, is provided with a cross tie member 13 having a cross section which is a duplicate of one-half the cross section of the orosstie member 12 between the rows. These half cross tie members preferably are, arranged near the same ends of the pins so that they are aligned with each other in the direction of the spacing of the rows of pins. These half sections-are such that, when two duplicate assemblies, such as described, are placed alongside each other with the cross tie members 13 parallel to each other, the members 13 at adjacent faces of the two assemblies engage each other and space the ad jacent rows of the two assemblies a distance apart equal to a spacing provided between the rows of each assembly by a "whole, cross tie .member 12. I Thus, the half cross tie members act both as cross ties for the pins andas spacers for the assemblies.

Any'number of such two'row assemblies may be disposed in spaced face to face parallel relation to build up pins is confined also between side walls, such as indicated in spaced relation above the row of pins a. The cross tie member d is engaged by any suitable guide roll 17 by which it is maintained in upright position'parallel to the cross" tie member 17. A'rotary welding electrode 18 of a conventional resistance welder, power driven in the direction indicated by the arrow 19, welds the work as it moves it from left to rightin FIG. 7. The rotary electrode is applied to the pins 0 successively, welding them to the cross tie member b in partially embedded relation therein, as described.

lel to the pin axes, through the innermost adjacent edges Referring to FIG. 7, the distance between planes, paralof cross tie members b and d at opposite faces of a given row of pins in a completed assembly, is constant. However, the pins to the right of a verticalpplane x-x through the axis of the welding electrode are already embedded in the cross tie member b, whereas those to the left of the plane x-.x lie with their lower faces juxtaposed against the'upper edge of the cross tie member b. Thus, instead of the axes of all of the pins of the row 0 lying in'a common plane, the axes of the pins already welded to the cross tie member b are coplanar, but those of the pins not yet welded are tilted upwardly in a direction, endwise of the pins, away from the member d,? and thus spaced, at their free ends, a distance above the axes they are to be embedded in the member b. Thus, as illustrated in FIG. 8, there is an angle VB between the plane of the axes of those pins to the right of plane x--x which are already welded and horizontal and the axes of those pins to the left of plane x-x which are not yet welded'but, instead, slope upwardly from their connections with the cross tie member d-to their points of engagement with the cross tie member 6. As illustrated in FIG. 6, if it should be attempted to bend the cross tie member fd about axes parallel to the pin axis to make up for this diiference as each successive pin passes under the electrode at xx and is embedded into the cross tie member fb, the cross tie member b, would have to bend the size of mat desired. By making the mat in assemblies of this nature, handling is facilitated-both during \manu-' facture of the assemblies and the installation of the mat The assemblies of pin fi-ns employing only whole cross t-ie members 2 are made, as illustrated: in FIGS. 6 through 8, by bonding a plurality of pins in a row in the spaced relation described to a common cross tie' member 2 arranged near the ends of the pins at oneface of the row of pins, but in substantially spaced relation to the ends of the pins at that face of the row. Only one cross tie member is applied to a row of pins originally, and any number of combinations of a row of pins with a cross tie member are i provided in a selected mat. As mentioned, the pins 1 are embedded part way into the cross tie members 2 during the welding operation, for example, for about one-third of the diameter of the pins. Each row of pins thus formed is welded to corresponding rows of pins also having welded thereto cross tie members 2, respectively. For convenience in effecting this operation, the pins of abruptly to an angle A and this bend would have to be relatively abrupt because of the close spacing 1 between twoadjacent'pins. However, because of its shape, the cross tie members are rigid edgewise and resistant to flex: ure in a direction of. the spacing of the rows of pins, or about axes parallel to the pin axes. I

Accordingly, therefore, thewelding equipment is arrangedso that instead of the cross tie member d flexing edgewise, it is held in proper vertical position but is caused, by pressure of the welding wheel at the free ends of the pins of the-row c, to twistand thus torsionally flex about its longitudinalaxis, relative to the portion to the left ofthe plane x-x in FIG. 6, which has not yet reached the weldingstation, to permit successivepins of the row 0 to-move into parallelism with the already welded pins of the row as they are welded to the cross tie member b.

If desired, as illustrated in FIG. 2, the cross tie members 2 maybe notched, as indicated at 20, midway between its points of connection with adjacent pins of its original row so that it can flex more readily in torsion to permit the dispos'itionof the pins of row clm the proper relation to the cross tie member b without greatly reducing its rigdity against flexure about its minor axes.

If a large number of rows are to be welded together by adding successive rows, a conventional weight supporting counterbalanced table may be disposed beneath the welding equipment to carry the increasing weight as each row is added.

As mentioned, in some instances it is desirable to make the initial assemblages in components wherein two rows of pins -11 are joined by a full width transverse tie member 12 and the transverse tie members '13 at the outermost faces of the two rows are half tie members, as illustrated in 'FIGS. 4 and 5. This arrangement is desirable not only for ease in handling during assembly, but also for'handling during welding into assemblages. In such instance, it is obvious that a cross tie member 12, such as indicated in FIGS. 9 and 10, may be passed longitudinally between two rotary welding electrodes 21 While guided by guides 22 and supported by supporting guide means '23, and rows of pins 11, already connected to tie bars 13, respectively, may be welded concurrently to the single tie rod -12. The original rows may be guided during welding by the supporting guide means 23. Spring pressed alignment guides 24 may be used to hold the pins in proper endwise position. Thus, each row of pins may be installed on its half cross tie member 13 in the same manner as heretofore de scribed for whole cross tie members 2. Next, two such rows of pins with their half cross tie members may be installed on the full cross tie member concurrently, as hereinbefore described.

Referring next to FIG. v11, a pin fin mat of the present invention including pins 1a and cross tie members 2a is shown as disposed between two walls 3a and 4a which are cylindrical and coaxial with each other. Heat exchangers often are made with such curvilinear walls and the present pin fin mats are particularly adapted for use in connection therwith, due to the fact that the tie members 2a are arranged near the ends of the pins with only one cross tie member disposed between adjacent rows of pins. The ends of the pins 1a of adjacent rows, opposite from their cross tie member at their other ends, are free for movement relatively toward each other by flexure of their cross tie member adjacent their other ends. Again, the cross tie member between two adjacent rows of pins is outwardly toward the radially outermost ends of the pins, and the cross tie member between each of the two rows of pins thus joined and the row next adjacent to it, is at the radially inward end of the pins of the two latter rows. Thus the mat can be flexed fiatwise to give it a curvilinear shape in which the pins extend generally radially of the uis of the walls 3a and 4a. For example, in every other row of pins, the radially innermost ends of the pins can be moved toward each other circumferentially of the walls 3a and 4a, so that the distance w between the centers of the inner ends of the pins circumferentially of the walls is less than the distance between their outer ends, the pins having been swung about the outermost tie member 2a. The distance y, of course, will be slightly greater than the original spacing of the pins due to this movement. On the other hand, as to the rows of pins joined by the radially inward tie members 2a, the distance x will be very slightly less than their original spacing, but the distance z considerably more than the original spacing. Thus, as to adjacent rows, the inner ends of the pins of one row are distance w apart which is less than the distance of the inner ends of the pins forming the next row, as indicated at x. At the outer ends, a distance y between the two pins joined by a radially outward tie member 2a is less than the distance z between two rows of pins joined by the inwardly disposed tie member 2a. Thus, a relatively stiff and rigid mat of pin fins is provided, but one which lends itself well to curving about an axis parallel to its faces and extending endwise of the cross tie members 2a, so as to dispose the pins radially, as described.

It is to be seen from the foregoing description that the present pin fin arrangement is quite satisfactory for rugged pin fin mats in which the pins are relatively stifi and in which stiff cross tie members are required for holding the pins in position and for spacing the rows apart. As mentioned, the resultant mat has the flexibility due to the fact that adjacent rows of pins are joined only near one side of the row and not at the other side, the cross tie members being alternately arranged whereby a certain amount of flexure of the rows about the ends joined to a cross tie member may be effected and the other ends are free to move relatively toward and away from each other.

This arrangement also has certain advantages in the expansion and contraction of the pin fin assemblage when in use in the heat exchanger.

Further, even though the cross tie member is extremely stiff in a direction of spacing of the rows of pins and the pins themselves are stiff, nevertheless a certain torsional flexure is utilized to permit the structure to be welded together properly with conventional resistance welding equipment of the rotary electrode type.

Having thus described my invention, 1 claim:

1. The method of making pin fin mats including the steps of forming an assemblage of pins by welding a plurality of relatively rigid pins in parallel closely spaced side by side relation to each other in a row to a first cross tie member at one face of the row near one edge of the row and extending lengthwise of the row and outwardly from the plane of said one face, the spacing of the pins and cross section of the cross tie member being preselected so that the cross tie member is highly resistant to flexure about axes parallel to the axes of the pins when it is welded to the pins, supporting a second cross tie member into position for resistance welding to the'pins of the assemblage, disposing the assemblage with its other face toward the second cross tie member, with the first cross tie member extending generally parallel to the second cross tie member, and with its pins free near their free ends and in position for welding to the second cross tie member, effecting relative passage of the assemblage and cross tie members concurrently endwise of the row of pins through a resistance welding station and, at said station, applying welding current to the pins and the second cross tie member and pressing the pins progressively, successively 'along the row as they pass said station, toward and embedding them near their free ends into the second cross tie members, causing accompanying torsional flexure of the first cross tie member, at that portion at and adjacent the welding station, about its longitudinal axis relative to that portion which has not yet reached the welding station until the surface of the assemblage facing toward the second cross tie member is generally parallel to the plane of the surface defined by the pins which have already been welded to both of the cross tie members.

2. The method according to claim 1 wherein the cross tie members are preselected with a cross section having a higher degree of rigidity against flexure about axes parallel to the pins than about axes normal to the plane of the row of pins to which they are connected.

3. The method according to claim 1 wherein adjacent pins of a row are arranged with their adjacent faces spaced apart a distance of about three times the thickness of their cross sections in a direction endwise of the row.

4. The method of making pin fin assemblies including the steps of forming at least two assemblages of pins, each -by resistance welding a plurality of relatively rigid pins, in parallel, closely spaced, side by side relation to each other in a row, to a cross tie member at one face of the row near one edge of the row with the member extending lengthwise of the row and outwardly from the plane of said one face, the spacing of the pins and cross section of the cross tie member being preselected so that the cross tie member is highly resistant to flexure about axes parallel to the axes of the pins when it is welded to the pins, supporting one. assemblage 'with its said one face exposed and accessible, disposing the other assemblage with its row of pins in spaced face to face relation to the row of pins of said one assemblage and with its said one face facing away from the said one face of the row of saidone assemblage and with, its cross tie member extending, lengthwise, generally parallel to the cross tie member of said, one asesmblage and with the pins of said other assemblage free at the ends opposite their cross tie member'and engaging, near their free ends, the

cross tie member of said one-assemblage, effecting relaw I tive passage of the assemblages concurrently endwise of the rows of pins through a resistance welding station, and:

at said station, applying welding current to the pinsof said other assemblage. and the cross tie member of said one assemblage, and concurrently pressing the pins of said other assemblage progressively, and successively along the row of pins, at the free ends of the pins toward, and embedding them'near their free ends into, the cross tie member of said one, assemblage, causing accompanying torsional flexure of the cross member of said other assem- I blage at the portionat and adjacent the welding station UNITED STATES PATENTS 2,298,250 Brown Oct.'6, 1942 2,678,808 Gier 'May 18, 1954 2,701,130 Boestad Feb. 1, 1955 2,809,276 Smith Oct. 8, 1957 2,892,618 'Holm June 30, 

1. THE METHOD OF MAKING PIN FIN MATS INCLUDING THE STEPS OF FORMING AN ASSEMBLAGE OF PINS BY WELDING A PLURALITY OF RELATIVELY RIGID PINS IN PARALLEL CLOSELY SPACED SIDE BY SIDE RELATION TO EACH OTHER IN A ROW TO A FIRST CROSS TIE MEMBER AT ONE FACE OF THE ROW NEAR ONE EDGE OF THE ROW AND EXTENDING LENGTHWISE OF THE ROW AND OUTWARDLY FROM THE PLANE OF SAID ONE FACE, THE SPACING OF THE PINS AND CROSS SECTION OF THE CROSS TIE MEMBER BEING PRESELECTED SO THAT THE CROSS TIE MEMBER IS HIGHLY RESISTANT TO FLEXURE ABOUT AXES PARALLEL TO THE AXES OF THE PINS WHEN IT IS WELDED TO THE PINS, SUPPORTING A SECOND CROSS TIE MEMBER INTO POSITION FOR RESISTANCE WELDING TO THE PINS OF THE ASSEMBLAGE, DISPOSING THE ASSEMBLAGE WITH ITS OTHER FACE TOWARD THE SECOND CROSS TIE MEMBER, WITH THE FIRST CROSS TIE MEMBER EXTENDING GENERALLY PARALLEL TO THE SECOND CROSS TIE MEMBER, AND WITH ITS PINS FREE NEAR THEIR FREE ENDS AND IN POSITION FOR WELDING TO THE SECOND CROSS TIE MEMBER, EFFECTING RELATIVE PASSAGE OF THE ASSEMBLAGE AND CROSS TIE MEMBERS CONCURRENTLY ENDWISE OF THE ROW OF PINS THROUGH A RESISTANCE WELDING STATION AND, AT SAID STATION, APPLYING WELDING CURRENT TO THE PINS AND THE SECOND CROSS TIE MEMBER AND PRESSING THE PINS PROGRESSIVELY, SUCCESSIVELY ALONG THE ROW AS THEY PASS SAID STATION, TOWARD AND EMBEDDING THEM NEAR THEIR FREE ENDS INTO THE SECOND CROSS TIE MEMBERS, CAUSING ACCOMPANYING TORSIONAL FLEXURE OF THE FIRST CROSS TIE MEMBER, AT THAT PORTION AT AND ADJACENT THE WELDING STATION, ABOUT ITS LONGITUDINAL AXIS RELATIVE TO THAT PORTION WHICH HAS NOT YET REACHED THE WELDING STATION UNTIL THE SURFACE OF THE ASSEMBLAGE FACING TOWARD THE SECOND CROSS TIE MEMBER IS GENERALLY PARALLEL TO THE PLANE OF THE SURFACE DEFINED BY THE PINS WHICH HAVE ALREADY BEEN WELDED TO BOTH OF THE CROSS TIE MEMBERS. 